Vellinga (1982); however, the good correspondence was found only in the surf zone. Offshore, the scaled-up 

 model results were substantially too shallow. For this case, Froude time scale appeared to govern the 

 transient response, i.e., similar profile development after same number of waves. Additional tests, 

 documented in an extended version of Dette and Uliczka (1986)^ utilized model bed material having grain 

 size of 0.17 mm. Comparisons again indicated the distortion given by Vellinga's guidance provided suitable 

 replication in the surf zone, but not in the offshore portion. Comparisons were also made using the 

 distortion required by Hughes's (1983) scaling criteria, with similar conclusions; but the comparison is not 

 strictly valid because the waves in the model were run according to the Froude criterion instead of the 

 shorter wavelength dictated by Hughes's distorted scaling of the hydrodynamics. Nonetheless, Dette and 

 Uliczka's results indicate that better similarity is achieved if the fall speed of the sediment is used in scaling 

 model results to the prototype. They also found that the initial profile shape seems to influence the final 

 bar configuration, but not the inshore portion of the profile. 



45. Fowler and Smith (1986) conducted small-scale movable-bed model tests to evaluate the validity of 

 five different sets of scaling criteria. The tests were aimed at reproducing both erosive and accretive profile 

 response documented for SavUle's (1957) large-scale experiments. Different bed materials used in the 



31 tests were sand (0.22 mm), crushed coal (1.2 mm), and glass beads (0.07 mm). Guidance suggested by 

 Vellinga (1982) performed well for both accretive and erosive conditions, whereas tests scaled according to 

 Hughes (1983) showed good correspondence only for erosive conditions. They questioned the distorting of 

 the Froude scaling criterion as required by Hughes's guidance. 



46. Fowler and Smith (1987) conducted additional small-scale tests using three sizes of sand grain and 

 scaling the models according to Vellinga's guidance. They found that best reproduction of prototype 

 observations were achieved with fine sand that allowed minimum model distortion. This is significant 

 because Vellinga's guidance approaches the guidelines spelled out by Dean (1985) when distortion is 

 minimized. 



47. Sayao and Nairn (1988) endorsed the scaling guidance outlined by Dean (1985) for beach profiles 

 by stating that the modeling requirements were ". . . necessary but not sufficient for dynamic similarity." 

 They suggested that, if possible, movable-bed model design should be geometrically undistorted with 

 Froude-scaled hydrodynamics and similarity of fall speed parameter between model and prototype. 

 However, it is necessary to quantify remaining scale effects due to dissimilar beach slopes and 

 nongeometrically scaled sediment diameters using prototype-scale results. They developed a morphological 

 time scale for onshore and longshore sediment transport rates by comparison of movable-bed model results 

 to numerical simulations, but they concluded (based on the work of Kriebel, Dally, and Dean 1986a) that 

 the time scale for erosive offshore transport was better represented by the Froude criterion. They noted 

 that validity of their proposed relationships was awaiting the availability of an adequate field data set. 



^Personeil communication, 30 September 1988, Dr. Klemens Uliczka, University of Hannover, Federal Republic of Germany. 



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